Most machinery shafts subject to rotation are supported between two or more bearings positioned at various locations along the shaft length. When such shafts as would be encountered in a turbocompressor are subject to high horsepower inputs and operate at rotational velocities on the order of 2000 r.p.m. and above, it is not uncommon to incur amplitudes of lateral vibration exceeding the usual tolerance of on the order of .+-.0.002 inches. Typically, the amplitudes of vibration at various axial shaft locations intermediate the bearings can be on the order of 0.01 inches and above. The eccentricity which results from those vibrations can produce various undesirable effects, not least of which is a rubbing contact between rotating elements on or near the shaft. An adverse effect on seals required for efficient operation of the machinery, including premature seal failure, is a typical consequence of such vibration.
For overcoming the adverse effects of vibration, various approaches have been undertaken including but not limited alone or in combination to increases in shaft diameter, material substitutions, mass reductions, use of special or increased number of bearings, special types and locations of oil seals where feasible, limiting operating speed of the equipment to exclude rotational velocities at which vibration tends to become severe, etc. Another approach frequently utilized almost as a last resort has been a limiting of shaft length requiring changes to the equipment that would otherwise be unnecessary. The latter frequently results in excessive manufacturing costs which either have to be absorbed or passed on to the customer.
While the mentioned approaches to the problem have amounted to an expedient, they have never been regarded as completely satisfactory. Yet despite recognition thereof a satisfactory solution has not heretofore been known.